Math Problem Statement

Express your answer as a polynomial in standard form. f, of, x, equals, x, squared, minus, x, minus, 1 f(x)= x 2 −x−1 g, of, x, equals, minus, x, minus, 4 g(x)= −x−4 Find: , f, of, g, of, x Find: f(g(x))

Solution

We are tasked with finding f(g(x))f(g(x)), where:

  • f(x)=x2x1f(x) = x^2 - x - 1
  • g(x)=x4g(x) = -x - 4

Step-by-step solution:

  1. Substitute g(x)g(x) into f(x)f(x):

    Since f(x)=x2x1f(x) = x^2 - x - 1, we replace every xx in f(x)f(x) with g(x)=x4g(x) = -x - 4.

    f(g(x))=(x4)2(x4)1f(g(x)) = (-x - 4)^2 - (-x - 4) - 1

  2. Simplify (x4)2(-x - 4)^2:

    Use the formula (a+b)2=a2+2ab+b2(a + b)^2 = a^2 + 2ab + b^2 where a=xa = -x and b=4b = -4.

    (x4)2=(x)2+2(x)(4)+(4)2(-x - 4)^2 = (-x)^2 + 2(-x)(-4) + (-4)^2 =x2+8x+16= x^2 + 8x + 16

  3. Substitute this into the equation:

    Now substitute the simplified form of (x4)2(-x - 4)^2 into the expression for f(g(x))f(g(x)):

    f(g(x))=(x2+8x+16)(x4)1f(g(x)) = (x^2 + 8x + 16) - (-x - 4) - 1

  4. Simplify further:

    Distribute the minus sign in the second term:

    f(g(x))=x2+8x+16+x+41f(g(x)) = x^2 + 8x + 16 + x + 4 - 1

  5. Combine like terms:

    f(g(x))=x2+9x+19f(g(x)) = x^2 + 9x + 19

Final answer:

f(g(x))=x2+9x+19f(g(x)) = x^2 + 9x + 19

Let me know if you need further details or clarification.

Here are 5 related questions for you to explore:

  1. What is g(f(x))g(f(x)) given the same functions?
  2. How do we find the inverse of f(x)f(x)?
  3. What is the vertex of the quadratic f(x)=x2x1f(x) = x^2 - x - 1?
  4. How do you find the domain and range of f(g(x))f(g(x))?
  5. How do you graph the composition f(g(x))f(g(x))?

Tip: When dealing with composition of functions, always start by substituting the inner function into the outer function's formula and then simplify step by step!

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Math Problem Analysis

Mathematical Concepts

Algebra
Function Composition
Polynomials

Formulas

f(x) = x^2 - x - 1
g(x) = -x - 4
f(g(x)) = f(-x - 4)

Theorems

Polynomial Simplification
Function Composition Theorem

Suitable Grade Level

Grades 9-12